Increasing deployment of digital television (satellite, cable and radio broadcast, as well as more recently IP multicast) provides more flexible content consumption on client side. Consumers may record television programs to watch them later to the diffusion time, or to make permanent private copies that can be used on any of their personal home devices. Sharing these copies with family or friends is another feature highly demanded by the digital TV subscribers.
However, these new services must guarantee the rights granted by the content owners or the service providers, as well as it must prevent any illegal usage and identify the successful hacking attempts.
To securely implement this kind of system, various technologies are known by the skilled man.
DTCP (Digital Transmission Content Protection) is a technical specification for copy protection of copyrighted content that is transferred over digital interfaces to personal home devices. Under this specification, digital content can be shared securely between devices in a user's home but not shared with third-parties outside the home network. Using an authentication scheme, DTCP allows the user to designate devices in the home network as trusted destinations that can transfer data back and forth.
However, the disadvantage of this technology is that a malicious user may circumvent the DTCP security measures by designing a “fake” device as being part of his home network and to use it not only to illicitly consume the content, but even worse, to illegal distribute the content.
Another disadvantage is that DTCP specifies that the content should be encrypted before being transmitted to other personal home devices. This requires more expensive personal home devices, so limiting the deployment of such a system.
CPCM (Content Protection and copy Management) is a part of DVB (Digital Video Broadcast) specification. CPCM addresses the protection of audiovisual content after it has been received by a consumer device. Once the audiovisual content is received by a CPCM-compliant device, it is protected by various cryptographic techniques and a license containing the consumption rights is bound to protected content. Therefore, the protected content can be rendered by other CPCM-compliant devices, with respect to the usage rights stored within the content.
While being two different technologies (CPCM is focusing on content protection and DTCP on transport link protection), CPCM suffers from the same disadvantages than DTCP: no possibility to identify the successful hacking attempts and complex and costly home devices to be deployed.
It could be helpful to resolve these disadvantages by marking the content with unique marks for every consuming devices to allow a later identification of eventual hacking attempts, while proposing a simpler protection system that requires a unique operation of content protection applied only once on the server side.